1. Technical Field
The disclosure relates to a resin composition, a multi-layered film including a cured product of the resin composition, a backsheet for photovoltaic modules including the same, a method of preparing the same, and a photovoltaic module including the same.
2. Related Art
Recently, there has been increasing interest in new regenerable energy and clean energy because of global environmental problems and exhaustion of fossil fuels. Among these, attention has been paid to solar photovoltaic energy as a representative clean energy source that can solve the environmental problems and the exhaustion of fossil fuels.
A solar cell to which a principle of solar photovoltaic power generation is applied is a device that converts sunlight into electric power, and is prepared in a unit type by performing various types of packaging processes for protecting the cell because it should be exposed to external environment for a long period to facilitate absorption of the sunlight, and the unit is called a photovoltaic module.
Generally, the photovoltaic modules use a backsheet with excellent weather resistance and durability to stably protect a solar cell in the state in which it is exposed to an external environment for a long period. The backsheet generally includes the backsheet laminating a resin layer including a fluorine-based polymer such as polyvinyl fluoride (PVF) on a substrate.
However, the PVF resin has a poor adhesive strength to a polyethylene terephthalate (PET) film that is typically used as a substrate of the backsheet so that a fluorine-based polymer film obtained from extruding or casting is laminated onto a substrate using a urethane-based adhesive and the like. However, the PVF resin has disadvantages in that it requires an expensive facility to manufacture a film; uses an adhesive; and further requires adhesive coating and laminating processes. In addition, the PVF resin has disadvantages in that a thicker film than the thickness of a film required for handling the film should be used in a film manufacturing process; it is limited to the use of various additives, fillers and the like; and requires high process-temperature.
In contrast, when a fluorine-based polymer film is prepared by coating and drying a resin suspension or solution on a substrate, a solvent having a high boiling point is generally used and a high drying temperature of at least 200° C. is required.
The PVF resin solution that requires a high drying temperature uses a great amount of energy to provide the high drying temperature, thereby increasing the manufacturing cost of the backsheet of photovoltaic modules and applying thermal shock to the substrate or causing thermal deformation to the substrate. Consequently, the quality (mechanical characteristics, etc.) of the product is degraded, and its mechanical properties rapidly deteriorate over a long-term outdoor use.
Accordingly, a backsheet material for a solar cell continues to be on demand because the backsheet material has excellent durability and weather resistance and also can be dried at low drying temperature, wherein the backsheet material can serve to improve the productivity and quality of the photovoltaic modules and can decrease the manufacturing cost of the photovoltaic backsheet.